How To Troubleshoot a Rock Tumbler (Fix Your Rock Tumbler)

Why Is My Rock Tumbler Not Working?

There’s nothing more frustrating than finally deciding to run a few batches of rocks through your trusty old rock tumbler. Perhaps everything starts out alright, but at some point during the tumbling process, things take a turn for the worse and your rock tumbler stops working.

But why is your rock tumbler not working? That’s exactly what this article is about. Let’s take a look at what’s happening with your rock tumbler and figure out how to fix it.

When it comes to rock tumblers, there are a couple issues that are by far the most common. Those common issues are:

  • A Leaking Barrel
  • A Barrel That Stops Turning

Related: Ultimate Guide To Rock Tumbling

Table of Contents

What To Do If Your Rock Tumbler Barrel is Leaking

how to fix leaking rock tumbler barrel

Inner Lid Not Seated Correctly

First, take a close look at your rock tumbler and make sure that the inner lid and barrel shoulder or rim are clean and free from debris. Then make sure that the inner lid is correctly seated on the rim inside the barrel.

Over Tightened Nut

Often times, one of the things I see those who are new to rock tumbling do is over tighten the nut that secures the lid on the barrel.

You simply want to tighten that nut with your fingers (finger tighten). Don’t use a wrench, pliers or any other tool to tighten the nut. If tightened too much, the edge of the lid will pry up off the rim of the barrel just enough that it doesn’t seat well and will lead to leaking.

Gas Build Up Inside The Barrel

When tumbling, some materials produce gas. When gas pressure builds up in the barrel, water will seep out around the lid’s edges.

You want to occasionally open of the lid to the barrel in order to allow the gas to escape.

Listed below are a number of substances that can create gas and cause spills according to

  1. man-made glass
  2. natural glass (especially obsidian)
  3. man-made slag
  4. pieces of metal
  5. pieces of metallic ore

Lid Is Cracked or Damaged

Plastic or fiberboard lids are common on some rock tumblers. The lid may have a rough edge due to a manufacturing flaw, or it may be the result of a lid being dropped or scraped against a hard surface.

To fix this issue, use an extra fine sandpaper to lightly sand the lid edges. Be careful not to sand the lid’s edges too much. Simply lightly rub the rim’s upper and lower edges. Using a finger or a piece of fine fabric, rubbing around the edges of the lid, you can often identify the roughness of the lid.

Be sure to wash the lid and the barrel before you put the barrel back together.

Lid Is Just Worn Out

Over time, the lids of rotary tumblers will begin to fall apart which is just a normal part of being used over and over again.

The lid of the tumbler is constantly scraped by grit and roughness as the tumbler spins. The middle of the lid will become increasingly thinner as a result of this over time. An unchecked and unreplaced lid might lead to an unsightly mess, if the leak isn’t noticed in time.

If this is the case, you’ll need to purchase a new lid.

Damaged Barrel

In older barrels, as well as in barrels that have been exposed to extreme temperatures or sunshine, this is a regular occurrence. The barrel’s rubber may develop small fractures or deform over time due to exposure to heat, cold, or sunlight.

Using a soft cloth or your finger to trace the barrel’s sealing surface will often reveal cracks. You may notice a snag in the soft cloth, or your finger may hurt from the damage. If you slightly flex the barrel rim, you may be able to see the damage. A new barrel is the sole solution to this issue.

The bottom of a well-used barrel rarely develops a hole. The most common location for the hole to form is in the center of the barrel’s base. A barrel full of rocks is turning, and this is the place at which the resulting friction is most concentrated. This necessitates the purchase of a new barrel.

What To Do If Rock Tumbling Barrel Stops Turning

What To Do If Rock Tumbling Barrel Stops Turning

Drive Belt Loose or Broken

A small but powerful motor and roller mechanism is what makes up the rotary rock tumbler. A thin rubber belt connects the motor to the drive roller which in turn causes the barrel to spin.

Over time this rubber belt can stretch out and become loose, which ultimately results in a barrel that no longer turns. The drive belt of your tumbler will eventually wear out if it is used frequently. As long as you own your tumbler, you’ll have to deal with that.

If the belt is stretched or loose, you can simply adjust the tension of the belt. Here is a good guide on how to adjust a rock tumbler belt.

Signs of a Loose Belt

A stretched belt will typically still spin the roller bars as it normally would, but once you place the barrel on the roller bars and add some resistance, the roller bars will stop spinning.

Signs of a Broken Belt

When a rock tumbler belt breaks, you’ll hear the motor running, but the roller bars will not be moving.

No Power To The Rock Tumbler

This one might seem really obvious, but you’d be surprised how often a lack of power to the tumbler is actually the culprit.

However, in addition to just making sure that the cord is plugged into the outlet, be sure to check all connections to any extension cords that you might be using.

Check to see if the outlet are GFCI protected. If so, make sure that the GFCI switch is turned on.

Finally, check the breakers in your breaker panel to make sure all of them are delivering power to the outlets. Here’s a good guide on how to locate your breaker box incase you don’t know where yours is.

The Barrel Is Too Heavy

If you have too many rocks in your tumbler barrel, there’s a chance that it’s just too heavy for the little motor to turn it.

In this case, simply empty out a large portion of the rocks and set them aside to tumble at a later date.

Every rock tumbler has a rated weight capacity. Check the manufacturer of your rock tumbler to find out what yours is.

Barrel Not Installed Correctly

Make sure that your barrel is properly installed and aligned correctly on the rock tumbler. Some rock tumblers are fairly precise on how they are to be installed on the rollers/motor.

Motor Runs Intermittently

If you’re noticing that the rock tumbler motor is cutting in and out, or will run for a short period of time and then stop, that’s usually a sign that the motor is bad. Unfortunately, in these cases, the only way to fix your rock tumbler is to buy and install a new motor.

Routine Rock Tumbler Maintenance

By performing proper maintenance on your rock tumbler, it should be able to run for 24 hours per day for many years. That is…if you properly maintain it.

Here’s a few things you can do to ensure the best results from your rock tumbler.


The motors on rock tumblers are designed for prolonged use and generally does not need to be oiled. You should also know that it is common for the motor on rock tumblers to run hot to the touch.


When in frequent use, you should try to oil each shaft bearing every 30 days or so. Simply apply one drop of a lightweight lubricating oil.

Drive Belt

Check to ensure that the drive belt is tight enough to turn the barrel without being too tight. If the belt is overtightened is a sure way to quickly stretch out the rubber belt as well as lead to bearing failure.

Routine Cleaning

Keep the outside of the barrel clean by wiping it down with a soapy wet cloth and rinse with clean water. Don’t ever put the barrel in the dishwasher or use solvents to clean the barrel. You don’t want to outside of the barrel to become to slick that the rollers are unable to spin the barrel. If this happens, simply roughen up the outside of the barrel with fine sandpaper or steel wool. That should add enough “grip” for the rollers.

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